1. Field of the Invention
The present invention relates generally to a device for detecting the angle of rotation and, more particularly, to the rotational angle detecting device for use in construction machinery and industrial machinery and capable of detecting the angle of rotation of a rotating element such as, for example, a rotary shaft or an oscillating shaft, while the latter is operated under a loaded condition.
2. Description of the Prior Art
As an instrument for measuring the angle of rotation of a rotary shaft or an oscillating shaft, a rotational angle detecting device has long been used. The rotational angle detecting device is a useful instrument as a means for measuring the absolute angle with respect to a reference point. The traditional rotational angle detecting device now in general use is of a structure shown in FIG. 7 and is in the form of a potentiometer including a resistor element 53 and an electroconductive brush 52 movable together with a rotary shaft 51 and held in sliding contact with the resistor element 53. This known rotational angle detecting device is so designed and so configured as to provide a signal of a voltage represented by the resistance of the resistor element 53 which varies depending on the position of the electroconductive brush 52.
In this known rotational angle detecting device, an oil retaining metal or a relatively small rolling contact bearing is employed to permit the rotary shaft 51 to be rotatably supported by a housing 54 and is unable to support a relatively high load such as brought about by the rotary shaft 51. When a relatively high load is imposed on the rotary shaft 51 in an axial or radial direction thereof, a relatively large error occurs in the detected angle of rotation and/or one or both of the resistor element 53 and the electroconductive brush 52 may be damaged. For this reason, where a rotatable mass element coupled with the rotary shaft 51 is relatively heavy and/or a load acts on the rotary shaft 51 of the potentiometer, means must be taken to avoid the load acting directly on the rotary shaft 51 and, for this purpose, a spring element or the like is generally employed to support the rotary shaft 51 during detection of the angle of rotation of the rotary shaft 51.